DOKK / manpages / debian 12 / libnvme-dev / nvme_uring_cmd.2.en
libnvme(2) API Manual libnvme(2)

struct nvme_uring_cmd - nvme uring command structure

struct nvme_uring_cmd {
__u8 opcode;
__u8 flags;
__u16 rsvd1;
__u32 nsid;
__u32 cdw2;
__u32 cdw3;
__u64 metadata;
__u64 addr;
__u32 metadata_len;
__u32 data_len;
__u32 cdw10;
__u32 cdw11;
__u32 cdw12;
__u32 cdw13;
__u32 cdw14;
__u32 cdw15;
__u32 timeout_ms;
__u32 rsvd2;
};

Operation code, see enum nvme_io_opcodes and enum nvme_admin_opcodes
Not supported: intended for command flags (eg: SGL, FUSE)
Reserved for future use
Namespace Identifier, or Fabrics type
Command Dword 2 (no spec defined use)
Command Dword 3 (no spec defined use)
User space address to metadata buffer (NULL if not used)
User space address to data buffer (NULL if not used)
Metadata buffer transfer length
Data buffer transfer length
Command Dword 10 (command specific)
Command Dword 11 (command specific)
Command Dword 12 (command specific)
Command Dword 13 (command specific)
Command Dword 14 (command specific)
Command Dword 15 (command specific)
If non-zero, overrides system default timeout in milliseconds
Reserved for future use (and fills an implicit struct pad
struct nvme_uring_cmd January 2023